Apparatus and method for attaching an integrated circuit sensor to a substrate

ABSTRACT

A method of fabricating an integrated circuit sensor package. The method comprises the steps of:  1 ) mounting a substrate on a first mold block, the substrate comprising a substantially planar material having a first substrate surface and a second substrate surface that contacts a mounting surface of the first mold block;  2 ) placing an adhesive on the first substrate surface;  3 ) placing an integrated circuit sensor on the adhesive; and  4 ) pressing a second mold block against the first substrate surface. The second mold block comprising a cavity portion for receiving the integrated circuit sensor, a contact surface surrounding the cavity portion, and a compliant layer mounted with the cavity portion. Pressing the second mold block against the first substrate surface causes the contact surface to form with the first substrate surface a seal surrounding the integrated circuit sensor. Pressing also causes the compliant layer to press against a sensor array surface of the integrated circuit sensor, thereby pressing the integrated circuit sensor into the adhesive and the first substrate surface.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention is generally directed to apparatuses andmethods for fabricating integrated circuit (IC) sensors and, morespecifically, to an apparatus and method for attaching an IC sensor to asubstrate.

BACKGROUND OF THE INVENTION

[0002] Many integrated circuit (IC) devices do not encapsulated theentire IC chip in a protective package. For example, an IC sensor chipused in a finger print reader is a touch chip device that uses a sensorarray to read a finger print. In order to work properly, the sensorarray must be at least partially exposed in order to receive the fingerof a user.

[0003] For these types of devices, it is necessary to package the ICsensor chip in such a way that the edges and wires of the IC sensor chipare protected, but the sensor array remains completely exposed. Thepackaging is usually accomplished using some kind of molding process.However, this process is made more difficult by the need to preventmolding flash from forming on the IC sensor and by the need tocompensate for variation in die thickness and die tilt. The exposed ICsensor brittle and must be handled carefully to prevent it fromshattering.

[0004] Therefore, there is a need in the art for improved processes forfabricating integrated circuit packages that contain an at leastpartially exposed integrated circuit sensor.

SUMMARY OF THE INVENTION

[0005] To address the above-discussed deficiencies of the prior art, itis a primary object of the present invention to provide a method offabricating an integrated circuit sensor package. According to anadvantageous embodiment of the present invention, the method comprisesthe steps of: 1) mounting a substrate on a first mold block, thesubstrate comprising a substantially planar material having a firstsubstrate surface on a first side and a second substrate surface on anopposing second side, such that the second substrate surface contacts amounting surface of the first mold block; 2) placing an adhesive on thefirst substrate surface; 3) placing an integrated circuit sensor on theadhesive; and 4) pressing a second mold block against the firstsubstrate surface, the second mold block comprising a cavity portion forreceiving the integrated circuit sensor, a contact surface surroundingthe cavity portion, and a compliant layer mounted with the cavityportion, wherein pressing the second mold block against the firstsubstrate surface causes the contact surface to form with the firstsubstrate surface a seal surrounding the integrated circuit sensor andfurther causes the compliant layer to press against a sensor arraysurface of the integrated circuit sensor, thereby pressing theintegrated circuit sensor into the adhesive and the first substratesurface.

[0006] According to one embodiment of the present invention, the methodfurther comprises the step of 5) injecting an encapsulant material intothe cavity portion of the second mold block.

[0007] According to another embodiment of the present invention, thecompliant layer forms a seal with the sensor array surface of theintegrated circuit sensor, thereby preventing the encapsulant materialfrom contacting the sensor array surface.

[0008] According to still another embodiment of the present invention,the method further comprises the steps of: 6) allowing sufficient timefor the adhesive and the encapsulant material to set, thereby fixing theintegrated circuit sensor to the first substrate surface and forming aprotective package that encapsulates the integrated circuit sensor whileleaving the sensor array surface exposed; and 7) removing the first andsecond mold blocks.

[0009] According to yet another embodiment of the present invention, themethod further comprises the step of 8) pressing a clamping blockassociated with the first mold block against a portion of the secondsubstrate surface opposite a position of the integrated circuit sensoron the first substrate surface.

[0010] According to a further embodiment of the present invention, thestep of pressing the clamping block against the portion of the secondsubstrate surface causes the first substrate surface to press againstthe integrated circuit and the adhesive, thereby pressing the sensorarray surface of the integrated circuit sensor more tightly against thecompliant layer The foregoing has outlined rather broadly the featuresand technical advantages of the present invention so that those skilledin the art may better understand the detailed description of theinvention that follows. Additional features and advantages of theinvention will be described hereinafter that form the subject of theclaims of the invention. Those skilled in the art should appreciate thatthey may readily use the conception and the specific embodimentdisclosed as a basis for modifying or designing other structures forcarrying out the same purposes of the present invention. Those skilledin the art should also realize that such equivalent constructions do notdepart from the spirit and scope of the invention in its broadest form.

[0011] Before undertaking the DETAILED DESCRIPTION OF THE INVENTIONbelow, it may be advantageous to set forth definitions of certain wordsand phrases used throughout this patent document: the terms “include”and “comprise,” as well as derivatives thereof, mean inclusion withoutlimitation; the term “or,” is inclusive, meaning and/or; the phrases“associated with” and “associated therewith,” as well as derivativesthereof, may mean to include, be included within, interconnect with,contain, be contained within, connect to or with, couple to or with, becommunicable with, cooperate with, interleave, juxtapose, be proximateto, be bound to or with, have, have a property of, or the like; and theterm “controller” means any device, system or part thereof that controlsat least one operation, such a device may be implemented in hardware,firmware or software, or some combination of at least two of the same.In particular, a controller may comprise a data processor and anassociated memory that stores instructions that may be executed by thedata processor. It should be noted that the functionality associatedwith any particular controller may be centralized or distributed,whether locally or remotely. Definitions for certain words and phrasesare provided throughout this patent document, those of ordinary skill inthe art should understand that in many, if not most instances, suchdefinitions apply to prior, as well as future uses of such defined wordsand phrases.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] For a more complete understanding of the present invention, andthe advantages thereof, reference is now made to the followingdescriptions taken in conjunction with the accompanying drawings,wherein like numbers designate like objects, and in which:

[0013]FIG. 1 illustrates an exemplary sensor mold prior to clampingaccording to one embodiment of the present invention;

[0014]FIG. 2 illustrates the exemplary sensor mold after clamping andinjection of an encapsulant material according to one embodiment of thepresent invention;

[0015]FIG. 3 is a flow diagram illustrating the exemplary moldingprocess according to one embodiment of the present invention; and

[0016]FIG. 4 illustrates an exemplary sensor package fabricated inaccordance with the principles of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0017]FIGS. 1 through 4, discussed below, and the various embodimentsused to describe the principles of the present invention in this patentdocument are by way of illustration only and should not be construed inany way to limit the scope of the invention. Those skilled in the artwill understand that the principles of the present invention may beimplemented in any suitably arranged integrated circuit mold.

[0018]FIG. 1 illustrates exemplary sensor mold 100 prior to clampingaccording to one embodiment of the present invention. Sensor mold 100comprises upper mold block 110, lower mold block 120, compliant layer130, clamp block 140, and shaft 150. In FIG. 1, sensor mold 100 is shownin the open position, before upper mold block 110 and lower mold block120 are pressed together. Substrate 190 is positioned on top of lowermold block 120. Integrated circuit (IC) sensor 160 is placed in adhesivelayer 170 for subsequent attachment to substrate 190. In a real worldenvironment, IC sensor 160 initially sits unevenly in adhesive 170 andis, therefore, not perfectly parallel to the surface of substrate 190,as depicted in FIG. 1.

[0019]FIG. 2 illustrates exemplary sensor mold 100 after clamping andinjection of encapsulant material 210 according to one embodiment-of thepresent invention. In FIG. 2, sensor mold 100 is shown in the closedposition, after upper mold block 110 and lower mold block 120 have beenpressed together and after shaft 150 has pressed clamping block 140against the bottom surface of substrate 190 immediately under theposition of IC sensor 160. The closure of upper mold block 110 and lowermold block 120 and the upward force F applied by shaft 150 presses ICsensor 160 into compliant layer 130. This causes compression ofcompliant layer 130 and distributes the pressure evenly across thesurface of IC sensor 160. Additionally, clamping block 140 is rotatablymounted by means of gimbal to the end of shaft 150, so that clampingblock 140 makes evenly distributed contact across the bottom surface ofsubstrate 190.

[0020]FIG. 3 depicts flow diagram 300, which illustrates the exemplarymolding process according to one embodiment of the present invention.Initially, substrate 190 is positioned on lower mold block 120 (processstep 305). Next, adhesive 170 is placed on substrate 190 and integratedcircuit sensor 160 is placed on adhesive 170 (process step 310). Whenintegrated circuit sensor 160 is in place, upper mold block 110 ispressed down on substrate 190 and integrated circuit sensor 160 (processstep 315). Additionally, clamp block 140 is pressed upwards on thereverse side of substrate 190 until the sensor surface is in contactwith upper mold block 110 (process step 320).

[0021] The force on integrated circuit 160 presses integrated circuit160 into compliant layer 130. This forms a tight seal, much like agasket. Next, encapsulant material 210 is injected into the cavity underupper mold block 110 (process step 325). After adhesive 170 andencapsulant material 210 are set, upper mold block 110 and lower moldblock 120 are removed and integrated circuit sensor 160 is ejected(process step 330).

[0022]FIG. 4 illustrates exemplary sensor package 405 fabricated inaccordance with the principles of the present invention. As FIG. 4shows, encapsulant material 210 surrounds integrated circuit sensor 160without covering the top surface of integrated circuit sensor 160. Forsimplicity, substrate 190 on which integrated circuit sensor 160 ismounted is not shown. Sensor array 405 on the top surface of integratedcircuit sensor 160 is exposed, thereby permitting sensor 405 tofunctions (i.e., read fingerprints, scan an object, and the like).

[0023] With the present invention, small changes in chip planarity andtilt are absorbed by the flexure of the integrated substrate in thegaps. Sufficient force (F) is applied by shaft 150 and clamping block140 to seal the sensor area against compliant layer 130 to preventmolding compound leakage. Clamping of the outer edge of the substrate isaccomplished in the usual way.

[0024] Upper mold block 110 preferably has a compliant surface, butcould also be a polished steel surface. Silicon rubber or a flurocarbonpolymer acts as a gasket on upper mold block 110 (i.e., touches the topsurface of the die). The sidewall-gap is critical for tilt compensation.Tool life is a major advantage of the present invention, if lower moldblock 120 was a solid piece, the gasket would wear out much quickerbecause silicon is very hard. In an alternative embodiment of thepresent invention, the entire assembly may be inverted such thatcompliant layer 130 may be on the lower mold rather than the top mold.

[0025] Although the present invention has been described in detail,those skilled in the art should understand that they can make variouschanges, substitutions and alterations herein without departing from thespirit and scope of the invention in its broadest form.

What is claimed is:
 1. A method of fabricating an integrated circuitsensor package comprising the steps of: mounting a substrate on a firstmold block, the substrate comprising a substantially planar materialhaving a first substrate surface on a first side and a second substratesurface on an opposing second side, such that the second substratesurface contacts a mounting surface of the first mold block; placing anadhesive on the first substrate surface; placing an integrated circuitsensor on the adhesive; and pressing a second mold block against thefirst substrate surface, the second mold block comprising a cavityportion for receiving the integrated circuit sensor, a contact surfacesurrounding the cavity portion, and a compliant layer mounted with thecavity portion, wherein pressing the second mold block against the firstsubstrate surface causes the contact surface to form with the firstsubstrate surface a seal surrounding the integrated circuit sensor andfurther causes the compliant layer to press against a sensor arraysurface of the integrated circuit sensor, thereby pressing theintegrated circuit sensor into the adhesive and the first substratesurface.
 2. The method as set forth in claim 1 further comprising thesteps of: allowing sufficient time for the adhesive to set, therebyfixing the integrated circuit sensor to the first substrate surface; andremoving the first and second mold blocks.
 3. The method as set forth inclaim 1 further comprising the step of injecting an encapsulant materialinto the cavity portion of the second mold block.
 4. The method as setforth in claim 3 wherein the compliant layer forms a seal with thesensor array surface of the integrated circuit sensor, therebypreventing the encapsulant material from contacting the sensor arraysurface.
 5. The method as set forth in claim 4 further comprising thesteps of: allowing sufficient time for the adhesive and the encapsulantmaterial to set, thereby fixing the integrated circuit sensor to thefirst substrate surface and forming a protective package thatencapsulates the integrated circuit sensor while leaving the sensorarray surface exposed; and removing the first and second mold blocks. 6.The method as set forth in claim 1 further comprising the step ofpressing a clamping block associated with the first mold block against aportion of the second substrate surface opposite a position of theintegrated circuit sensor on the first substrate surface.
 7. The methodas set forth in claim 6 wherein the step of pressing the clamping blockagainst the portion of the second substrate surface causes the firstsubstrate surface to press against the integrated circuit and theadhesive, thereby pressing the sensor array surface of the integratedcircuit sensor more tightly against the compliant layer.
 8. The methodas set forth in claim 7 further comprising the steps of: allowingsufficient time for the adhesive to set, thereby fixing the integratedcircuit sensor to the first substrate surface; and removing the firstand second mold blocks.
 9. The method as set forth in claim 7 furthercomprising the step of injecting an encapsulant material into the cavityportion of the second mold block.
 10. The method as set forth in claim 9wherein the compliant layer forms a seal with the sensor array surfaceof the integrated circuit sensor, thereby preventing the encapsulantmaterial from contacting the sensor array surface.
 11. The method as setforth in claim 10 further comprising the steps of: allowing sufficienttime for the adhesive and the encapsulant material to set, therebyfixing the integrated circuit sensor to the first substrate surface andforming a protective package that encapsulates the integrated circuitsensor while leaving the sensor array surface exposed; and removing thefirst and second mold blocks.
 12. An integrated circuit sensor packagefabricated by the process steps set forth in claim
 1. 13. An integratedcircuit sensor package fabricated by the process steps set forth inclaim
 2. 14. An integrated circuit sensor package fabricated by theprocess steps set forth in claim
 3. 15. An integrated circuit sensorpackage fabricated by the process steps set forth in claim
 4. 16. Anintegrated circuit sensor package fabricated by the process steps setforth in claim
 5. 17. An integrated circuit sensor package fabricated bythe process steps set forth in claim
 6. 18. An integrated circuit sensorpackage fabricated by the process steps set forth in claim
 7. 19. Anintegrated circuit sensor package fabricated by the process steps setforth in claim
 8. 20. An integrated circuit sensor package fabricated bythe process steps set forth in claim
 9. 21. An integrated circuit sensorpackage fabricated by the process steps set forth in claim
 10. 22. Anintegrated circuit sensor package fabricated by the process steps setforth in claim
 11. 23. A mold for fabricating an integrated circuitsensor package comprising: a first mold block comprising a mountingsurface for mounting thereon a substrate, said substrate comprising asubstantially planar material having a first substrate surface on afirst side and a second substrate surface on an opposing second side,wherein said second substrate surface contacts said mounting surface ofsaid first mold block; a second mold block comprising: 1) a cavityportion suitable for receiving an integrated circuit sensor disposed onsaid first substrate surface; 2) a contact surface surrounding saidcavity portion suitable for forming a seal with said first substratesurface; and 3) a compliant layer mounted with said cavity portion,wherein pressing said second mold block against said first substratesurface causes said contact surface to form said seal with said firstsubstrate surface, wherein said seal surrounds said integrated circuitsensor, and wherein pressing further causes said compliant layer topress against a sensor array surface of said integrated circuit sensor.